The present invention relates to the field of electronic imaging devices, and more particularly to a method and apparatus for precision placement of an imaging device such as a liquid crystal display (xe2x80x9cLCDxe2x80x9d) imaging device. The predominant current usage of the inventive mechanical convergence device is in the precision positioning of reflective imaging devices in a multi channel projection system, wherein it is particularly important to maintain a precise relationship between a plurality of such imaging devices.
Projection type imaging devices commonly use micro LCD imagers. Since the pixel size and spacing on these are so small, they must be precisely placed in relation to the surface whereon they are mounted, and in relation to each other. In a liquid crystal projector, white source light is separated into beams of its three primary colors. Each beam is then infused with an image by a liquid crystal light valve or micro-LCD. Finally, the three beams are recombined into a single image and projected onto a display device (a screen).
The micro LCD""s generate a representation of the image to be projected by using many small picture elements referred to as pixels. Therefore, the above mentioned beams of light that emerge from the micro-LCD""s are pixellated representations of the particular color components of the image. Thus, an accurate projected image requires that the pixels of the three infused beams be precisely aligned during the recombination step, meaning that the micro-LCD""s themselves must be carefully positioned. In order to optimally orient the micro-LCD""s the following requirements must be met.
(1) 6 degree of freedom (dof) adjustment capability must be available. Both rotation and linear translation with respect to three perpendicular axes are required in order to ensure that proper image alignment can be achieved.
(2) Adjustment mechanisms must have high resolution controls. Because of the small size of the pixels, direct manual adjustments are too crude to achieve proper alignment. Some sort of interface must be provided which can transform relatively large-scale operator inputs into micro-imager motions of a magnitude commensurate with the pixel size.
(3) Adjustment mechanisms must provide positive positioning constraints. Since multiple operations are required to tune all 6 degrees of freedom, intermediate adjustments must have some amount of resistance to motion. Positioning devices typically have some sort of final locking mechanism, but to activate and deactivate that mechanism numerous times over the course of adjustment is cumbersome and often impossible. Therefore, any robust positioning device must provide for physical locating effects, rather than relying on balance, gravity or friction.
(4) The individual magnification of each image must be independently adjustable. There must be a means for making slight adjustments to the projected size of the image from any projection device. This means must be simple, inexpensive, and easy to use such that adjustments can be made quickly during the production process.
In order to accomplish this precise positioning, very precise alignment mechanisms have been developed to carefully position LCD imagers in relation to the common housing. However, there remains the problem of how to hold the imager in position permanently after the alignment mechanism has so precisely temporarily positioned it. It is known in the art to use clear plastic interface parts to maintain thin bond gaps and still permit multi-axis alignment of an imaging device relative to a fixed housing. These interface parts are usually added to the assembly at an integration stage, and need to be restrained into the assembly during the alignment process. In the prior art there have usually been at least two of such parts and they have been cumbersome to handle simultaneously. Special tooling is required to assemble them. Also the tooling may require that the clear interface parts be held in place with an external spring. All of this requires additional time and effort.
It would be advantageous to have something that could be used to hold a micro LCD imager permanently in position on a housing after it is precisely aligned that is inexpensive and easy to manufacture and to use, and which will hold the imager rigidly and securely in position. However, to the inventor""s knowledge, all prior art methods and means have involved multiple parts which are cumbersome and time consuming to apply.
Accordingly, it is an object of the present invention to provide a method and apparatus for mounting an imaging device on a housing which is easy to use.
It is another object of the present invention to provide a method and apparatus for mounting an imaging device on a housing which will hold the imaging device securely and permanently in place.
It is still another object of the present invention to provide a method and apparatus for mounting an imaging device on a housing which is inexpensive to manufacture and to use.
It is yet another object of the present invention to provide a method and apparatus for mounting an imaging device on a housing which will reduce the overall cost of producing a multi beam projection apparatus.
One embodiment of the invention is a single part that straddles the assembly to be converged. In the presently described embodiment of the invention the single part is made of clear plastic. It has a frame that is adapted to be pushed against a fixed housing. Fingers protrude from the frame and cradle the assembly to be converged. The fingers have tips on them that interlock with the assembly and make the interface part captive. A small leaf flexure provides some force away from the assembly, and pushes the frame against the fixed housing when the assembly is moved into position with respect to the fixed housing. The clearances between the frame and the aligned assembly are small. When the assembly is aligned, a small amount of adhesive is allowed to wick into the small gaps. There is also a small gap between the frame and fixed housing. Adhesive is applied and allowed to wick into this gap, as well. The overall result is that there is complete 6-axis freedom of alignment. The bond gaps are kept to a minimum so the adhesive shrinkage has no appreciable effect on the alignment.
It is an object of the present invention to provide a method and apparatus for holding an LCD imager in place precisely as positioned.
It is a further object of the present invention to provide a method and apparatus for holding an LCD imager in place which is easy to apply.
It is still another object of the present invention to provide a method and apparatus for holding an LCD imager in place which is inexpensive to manufacture and to use.
It is yet another object of the present invention to provide a method and apparatus for holding an LCD imager in place which result in a well attached imager.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of modes of carrying out the invention, and the industrial applicability thereof, as described herein and as illustrated in the several figures of the drawing. The objects and advantages listed are not an exhaustive list of all possible advantages of the invention. Moreover, it will be possible to practice the invention even where one or more of the intended objects and/or advantages might be absent or not required in the application.
Further, those skilled in the art will recognize that various embodiments of the present invention may achieve one or more, but not necessarily all, of the above described objects and advantages. Accordingly, the listed advantages are not essential elements of the present invention, and should not be construed as limitations.